Contents lists available at ScienceDirect Environmental Research journal homepage: www.elsevier.com/locate/envres Vacuum ultraviolet irradiation for mitigating dissolved organic nitrogen and formation of haloacetonitriles Pradabduang Kiattisaksiri a,b,h , Eakalak Khan c , Patiparn Punyapalakul d , Charongpun Musikavong e , Daniel C.W. Tsang f , Thunyalux Ratpukdi g,h,* a Faculty of Public Health, Thammasat University (Lampang Center), Lampang, 52190, Thailand b International Program in Hazardous Substance and Environmental Management, Graduate School, Chulalongkorn University, Bangkok, 10330, Thailand c Department of Civil and Environmental Engineering and Construction, University of Nevada, Las Vegas, Las Vegas, NV, 89154-4015, United States d Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, 10330, Thailand e Environmental Assessment and Technology for Hazardous Waste Management Research Center, Department of Civil Engineering, Faculty of Engineering, Prince of Songkla University, Hatyai, Songkhla, 90112, Thailand f Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China g Department of Environmental Engineering, Faculty of Engineering, and Research Center for Environmental and Hazardous Substance Management, Khon Kaen University, Khon Kaen, 40002, Thailand h Center of Excellence on Hazardous Substance Management (HSM), Chulalongkorn University, Bangkok, 10330, Thailand ARTICLE INFO Keywords: Dissolved organic nitrogen (DON) Fluorescence excitation-emission matrix (FEEM) Haloacetonitrile formation potential (HANFP) Nitrogenous disinfection by-products (N-DBPs) Vacuum ultraviolet (VUV) ABSTRACT The main objective of this work was to investigate the feasibility of using vacuum ultraviolet (VUV, 185 + 254 nm) and ultraviolet (UV, 254 nm) for the reduction of dissolved organic nitrogen (DON) and ha- loacetonitrile formation potential (HANFP) of surface water and treated effluent wastewater samples. The results showed that the reduction of dissolved organic carbon (DOC), DON, hydrophobicity (HPO), absorbance at 254 nm (UV 254 ), and fluorescence excitation-emission matrix (FEEM) of both water samples by VUV was higher compared to using UV. The addition of H 2 O 2 remarkably improved the performances of VUV and UV. VUV/H 2 O 2 exhibited the highest removal efficiency for DOC and DON. Even though HANFP increased at the early stage, its concentration decreased (19–72%) at the end of treatment (60 min). Decreases in DON (30–41%) and DOC (51–57%) led to HANFP reduction (53–72%). Moreover, FEEM revealed that substantial reduction in soluble microbial product-like compounds (nitrogen-rich organic) had a strong correlation with HANFP reduction, implying that this group of compounds act as a main precursor of HANs. The VUV/H 2 O 2 system significantly reduced HANFP more than UV/H 2 O 2 and therefore is suitable for controlling HAN precursors and HAN for- mation in drinking water and reclaimed wastewater. 1. Introduction Haloacetonitriles (HANs) are an emerging group of nitrogenous disinfection by-products (N-DBPs). During the past decade, HANs have attracted attention due to of their high toxicity, which is approximately two orders of magnitude higher than regulated haloacetic acids (HAAs) (Muellner et al., 2007). HANs can be formed via reactions between typical disinfectants (chlorine and chloramine) and natural organic matter (NOM). The organic nitrogen portion of NOM (measured as dissolved organic nitrogen, DON) is known as a precursor of HANs as well as other N-DBPs such as N-nitrosodimethylamine (NDMA), halo- nitromethanes (HNMs), and haloacetamides (HAcAms) (Yimeng et al., 2017; Han et al., 2018; Chuang et al., 2019). The presence of DON raises a concern regarding N-DBPs in both drinking water as well as reclaimed water. In surface water, DON concentration ranges from 0.07 to 0.62 mg-N/L with a median value of 0.30 mg-N/L (Xu et al., 2011; Krasner et al., 2012; Chu et al., 2014). For secondary wastewater effluent, DON concentration ranges from 0.30 to 3.33 mg-N/L (Pehlivanoglu-Mantas and Sedlak, 2008; Chen et al., 2011a; Huang et al., 2012; Simsek et al., 2013). DON in drinking water sources can result from agricultural runoff, treated wastewater effluent, excretion from algae, and/or background NOM. For potable water reuse, treated wastewater effluent requires proper treatment for DON removal prior to disinfection to limit N-DBPs. https://doi.org/10.1016/j.envres.2020.109454 Received 2 December 2019; Received in revised form 29 February 2020; Accepted 26 March 2020 * Corresponding author. Department of Environmental Engineering, Faculty of Engineering, and Research Center for Environmental and Hazardous Substance Management, Khon Kaen University, 123 Mitrapap Road, Muang District, Khon Kaen, 40002, Thailand. E-mail address: thunyalux@kku.ac.th (T. Ratpukdi). Environmental Research 185 (2020) 109454 Available online 02 April 2020 0013-9351/ © 2020 Elsevier Inc. All rights reserved. T